An NMR study and crystal structure of [{cis-Pt(NH_3)_2(9EtG-#kappa#N~7)}_2-(#mu#-pz)][NO_3]_3 (9EtG = 9-ethylguanine) as a model compound for the 1,2-intrastrand GG crosslink

摘要

The platinum(II) complex [{cis-Pt(NH_3)_2(9EtG-#kappa#N~7)}_2(#mu#-pz)][NO_3]_3 centre dot 4H_2O 2 (pz = pyrazolate, 9EtG = 9-ethylguanine) was prepared from [{cis-Pt(NH_3)_2}_2(#mu#-OH)(#mu#-pz)][NO_3]_2 1 and 9EtG. It was characterized by ~1H and ~(195)Pt NMR, and a crystal structure determination was performed. All ~1H NMR chemical shifts from the 9EtG ligands are observed at higher fields compared with those of free 9EtG, which is ascribed to their stacking interaction. The two 9EtG ligands are in a head-to-head orientation, and two intramolecular hydrogen bonds are observed between the ammine ligands and O~6 oxygen atoms of the 9EtG ligands. The dihedral angle between the guanine planes is 10.8 deg C, and the average distance is 3.89 A.